System, method and apparatus for tolerance ring with functional layers

ABSTRACT

A tolerance ring with functional layers has an annular band and an elastomeric layer. The assembly also may have a low friction layer, which may be bonded, calendared or laminated thereto. The low friction material may completely encapsulate the annular band.

This application claims priority to and the benefit of U.S. Prov. Pat.App. No. 61/287,732, filed on Dec. 18, 2009, and is incorporated hereinby reference in its entirety.

FIELD OF THE DISCLOSURE

The invention relates in general to tolerance rings that are locatedbetween moving parts and, in particular, to an improved system, methodand apparatus for a tolerance ring with functional layers.

BACKGROUND

Tolerance rings constrain movement between parts that move relative toeach other, such as rotating shafts in housing bores. One type oftolerance ring is an annular band located in the gap between the outersurface of a shaft and the inner surface of a bore. This tolerance ringlimits radial or axial motion of the shaft within the bore while stillpermitting relative movement.

In conventional tolerance ring configurations, a close fit is soughtbetween the inner and outer components. In addition, either forces forproviding maximal frictional engagement or minimal variation in slidingforces are sought. A close fit between the components is desirablebecause it reduces relative vibration between the parts. Thus, tolerancerings are able to compensate for tolerances or misalignments, createtorque and can improve other properties, such as noise, vibration andharshness (NVH) properties. Torque and even NVH are mainly influenced bythe material properties of common tolerance rings, which are usuallyformed only from stainless steel. These requirements between the innerand outer components require strong and substantial contact, whichincreases frictional forces. Although these solutions are workable forsome applications, improvements in tolerance rings continue to be ofinterest.

SUMMARY OF THE INVENTION

Embodiments of a system, method and apparatus for tolerance rings withfunctional layers are disclosed. In some versions, a tolerance ringassembly comprises an outer component, an inner component located in theouter component that is movable relative thereto, and a tolerance ringmounted between the inner and outer components. The tolerance ring maycomprise a metallic annular band and an elastomeric layer secured to themetallic layer.

In other embodiments, the assembly further comprises a low frictionlayer on at least one of the annular band and the elastomeric layer. Theannular band may be formed from spring steel and the low friction layermay be laminated to at least one side of the annular band to improvesliding properties of the tolerance ring. The low friction layer may belocated on the annular band opposite the elastomeric layer. The lowfriction layer may comprise PTFE and be bonded to the annular band orthe elastomeric layer. The assembly may further comprise an adhesive orprimer layer between the annular band and the elastomeric layer.

In still other embodiments, the tolerance ring comprises an annular bandformed from a metallic material having radial inner and outer surfaces.The low friction material encapsulates the annular band, such that boththe radial inner and outer surfaces are located substantially completelywithin the low friction material. The annular band may be locatedcompletely within the low friction material such that no portion or onlysome portion of the annular band is exposed from and external to the lowfriction material. The annular band may comprise spring steel and beperforated or stamped. The annular band may comprise geometricalformations such as waves that are formed therein by coining or deepdrawing. Moreover, the annular band may be encapsulated within the lowfriction material by calendaring or laminating.

In some embodiments, the low friction material may form a smoothcylindrical profile, and the annular band undulates in a non-cylindricalprofile within the smooth cylindrical profile. The low friction materialand the annular band each may have non-cylindrical profiles and becomplementary in shape to each other. The tolerance ring may furthercomprise a backing layer joined to the tolerance ring.

In additional embodiments, a method of forming a tolerance ringcomprises providing a sheet formed from a metallic material, formingapertures in the sheet, fabricating geometrical formations into thesheet to form a sheet profile; encapsulating the sheet profile in a lowfriction material, and forming the encapsulated sheet profile into anannular shape to form a tolerance ring. The annular band may have radialinner and outer surfaces with the low friction material encapsulatingthe annular band, such that both the radial inner and outer surfaces aresubstantially located within the low friction material. The method mayfurther comprise forming shapes in the low friction material that arecomplementary in shape to the geometrical formations in the sheetprofile.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure may be better understood, and its numerousfeatures and advantages made apparent to those skilled in the art byreferencing the accompanying drawings.

FIGS. 1A and B are top and sectional side views of one embodiment of aperforated metallic sheet constructed in accordance with the invention;

FIGS. 2 and 3 are sectional side views of other embodiments of formedversion of the perforated metallic sheet constructed in accordance withthe invention;

FIGS. 4 and 5 are sectional side views of still other embodiments ofencapsulated, formed, perforated metallic sheet constructed inaccordance with the invention;

FIGS. 6 and 7 are sectional side views of additional embodiments ofencapsulated, formed, perforated metallic sheet constructed inaccordance with the invention;

FIGS. 8 and 9 are sectional side views of other embodiments ofencapsulated, formed, perforated metallic sheet constructed inaccordance with the invention;

FIG. 10 is an isometric view of the embodiment of FIG. 5 and isconstructed in accordance with the invention;

FIG. 11 is a sectional side view of an embodiment of a tolerance ringconstructed in accordance with the invention;

FIGS. 12A, B and C are sectional side views of other embodiments oftolerance rings constructed in accordance with the invention;

FIG. 13 is a sectional side view of another embodiment of a tolerancering constructed in accordance with the invention; and

FIGS. 14A, B and C are sectional side views of still other embodimentsof tolerance rings constructed in accordance with the invention.

The use of the same reference symbols in different drawings indicatessimilar or identical items.

DESCRIPTION OF THE DRAWINGS

Embodiments of a system, method and apparatus for tolerance rings withfunctional layers are disclosed in FIGS. 1-14. For example, FIGS. 12-14depict a tolerance ring assembly 21 comprising an outer component 23having a bore 25 with an axis therein. An inner component 27 is mountedin the bore 25 of the outer component 23 and has an outer surface 29.The inner component 27 mates with the outer component 23 and is movablerelative thereto. A tolerance ring 31 is located in the bore 25 betweenthe inner and outer components 23, 27. The tolerance ring 31 comprisesan annular band 33 formed from a metallic material, an elastomeric layer35 on the annular band 33, and a low friction layer 37 (FIG. 13) on atleast one of the annular band 33 and the elastomeric layer 35.

The annular band 33 may be formed from spring steel and the low frictionlayer 37 may be laminated to at least one side of the annular band. Thelow friction layer 37 may be located on the annular band 33 opposite theelastomeric layer 35, as shown in FIG. 13. The low friction layer 37 maycomprise PTFE and be bonded with a glue or adhesive 39 to one of theannular band 33 and the elastomeric layer 35. The elastomeric layer maycomprise, for example, nitrile rubber, olefinic elastomeric,polyether-/polyester-elastomeric, ethylene-propylene-elastomeric,ethylene-acrylic rubber and fluoro elastomeric materials. The adhesive39 also may comprise a primer between the annular band 33 and theelastomeric layer 35, and between the low friction layer 37 and theannular band and/or elastomeric layer.

Referring now to FIG. 11, embodiments also may comprise an assembly 51having an outer component 53, an inner component 55 located in the outercomponent 53 that is movable relative thereto. A tolerance ring 61 ismounted between the inner and outer components 53, 55. The tolerancering comprises an annular band 63 formed from a metallic material andhaving radial inner and outer surfaces 65, 67. A low friction material71 encapsulates the annular band 63, such that both the radial inner andouter surfaces 63, 65 are substantially located within the low frictionmaterial 71.

As shown in FIGS. 8 and 9, the band 63 may be located completely withinthe low friction material 71 such that no portion of the band 63 isexposed from and external to the low friction material 71. In otherembodiments (FIGS. 4-7), at least a portion of the band 63 is exposedfrom and extends externally relative to the low friction material 71.The band 63 may be formed from spring steel and may be perforated orstamped 73, as shown in FIGS. 1A and 1B. FIGS. 2 and 3 illustrate thatthe band 63 may comprise geometrical formations 75 that are formedtherein by coining or deep drawing. The geometrical formations 75 maycomprise waves, cones or ball-shaped formations, as shown in FIGS. 4 and5. The band 63 may be encapsulated within the low friction material bycalendaring and sintering (FIGS. 4-7) or laminating (FIGS. 8 and 9). Asshown in FIGS. 8 and 9, the low friction material 71 laminated to theband 63 may comprise a PTFE compound tape.

In some embodiments, (FIGS. 4, 5 10 and 11), the low friction material71 may form a smooth profile (e.g., cylindrical in its final form inFIG. 11), such that the band 63 undulates in a non-cylindrical profilewithin the smooth cylindrical profile of material 71. In otherembodiments (FIGS. 6-9), both the low friction material 71 and the band63 each have non-cylindrical profiles and are complementary in shape toeach other.

The embodiment of FIG. 11 further comprises a backing layer 77 that isjoined to the tolerance ring assembly 61. The backing layer 77 may beformed from, for example, steel, Al, Cu and Ti, and is radially externalto the low friction layer 71. In some embodiments, the low frictionlayer 71 is laminated on the backing layer 77. In some versions, the lowfriction layer may comprise a thickness of approximately 0.1 to 0.05 mmon each of the radial inner and outer surfaces 65, 67 of the band 63.Moreover, the low friction layer 71 may be bonded or welded to the band63.

In still other embodiments, a method of forming a tolerance ringcomprises providing a sheet formed from a metallic material; formingapertures in the sheet; fabricating geometrical formations into thesheet to form a sheet profile; encapsulating the sheet profile in a lowfriction material; and forming the encapsulated sheet profile into anannular shape to form a tolerance ring.

The aperture formation may comprise forming shaped holes in the sheet byperforating or stamping. The fabricating of geometrical formations intothe sheet may be accomplished by coining, forming or deep drawing waves,balls or cones to form the sheet profile. The encapsulating step may beperformed in the sheet profile in the low friction material bycalendaring or laminating through the apertures in the sheet. The sheetmay be formed into an annular band having radial inner and outersurfaces. The low friction material encapsulates the annular band suchthat both the radial inner and outer surfaces are located within the lowfriction material.

The method may further comprise, after encapsulation, forming shapes inthe low friction material that are complementary in shape to thegeometrical formations in the sheet profile. The forming shapes step maycomprise coining, calendaring and/or sintering the low frictionmaterial. The fabricating and encapsulating steps may occur before orafter each other, and the encapsulation may occur via lamination. Themethod may further comprise installing a backing layer to the tolerancering, such as on a radial exterior of the low friction layer.

The embodiments disclosed herein have significant advantages overconventional solutions. For example, the combination of a tolerance ringand an elastomeric backing improves the design of tolerance rings withsofter performance. The term soft is used in terms of providing torqueat a lower level with less variation. In terms of NVH, these materialssignificantly decouple the two mating parts that are connected by thetolerance ring without diminishing other areas of performance. As aresult, these designs significantly reduce noise and vibration.

In another example, a metallic material with spring behavior is coatedwith an adhesive and/or primer and combined with an elastomeric layer toform a composite material. The metal may comprise, e.g., stainlesssteel, carbon steel or other resilient metals. The elastomeric backingmay comprise, e.g., nitrile rubber, neoprene rubber, silicone rubber,olefinic elastomeric, polyether-/polyester-elastomeric,ethylene-propylene-elastomeric, ethylene-acrylic rubber and/or fluoroelastomeric. In other embodiments, the tolerance ring may comprise aninner metallic layer and an external elastomeric layer.

In other embodiments, a sliding or low friction layer is added to thestructure. These designs improve the sliding properties of the tolerancecompensating element. For example, the low friction material maycomprise PTFE on the elastomeric layer, and/or even on the metal sideopposite to the elastomeric layer. Like the elastomeric layer, the lowfriction layer also may be bonded to the tolerance ring (e.g., eitherthe metallic or elastomeric layer) with an adhesive or glue.

In still other embodiments, a resilient metallic layer is laminated witha low friction material. The metal surface may then be coated with anadhesive and/or primer and combined with an elastomeric layer to form acomposite material. Other combinations also are possible. Someembodiments include a tolerance ring that is completely encapsulated bythe low friction layer compound. For example, a composite structurehaving a perforated metallic core formed from spring steel is completelyencapsulated with PTFE.

Both the composition and the production method are different from aconventional sliding bearing, and also different from a conventionaltolerance ring. With the described encapsulated tolerance ring severaldifferent functions are provided. These embodiments act as a slidingbearing with additional tolerance compensation, a defined torque can beapplied, and they work as tolerance rings with improved frictionproperties.

As a substrate or an intermediate layer, a spring steel material sheetor coil may be first perforated, then shaped (e.g., in waves, ball-likeshapes, and/or other deep-drawn or coined shapes). These shaped areasmay be regularly distributed and formed closely together. Thus, in someembodiments, there are as many waves on these tolerance rings as onconventional tolerance rings. In some embodiments, the spring steel coreis fully embedded or encapsulated so that the resulting compound stripshows no waviness at all, and appears as a block-like shape.

The encapsulation may be achieved, for example, by a calendaring processor through laminating a tape onto the steel core. Optionally, in thelatter case, a strong backing material may be added to the structure orcore to make the bearing capable for press fitting in housings.

General applications for embodiments of this composite structure may beused to produce sliding bearings for clearance-free or clearance-reducedapplications, or to produce tolerance rings with low retention force.The metallic core formed from spring steel acts as a spring and thusprovides the tolerance adjustment between the bearing surface and, e.g.,a shaft by using the low friction compound-coated spring waves. The lowfriction layer may engage only the functional side of the shaft orcounterpart. Alternatively, it may engage both components, and/orprovide a retention force needed between the mating components. The lowfriction layer allows the composite structure to work as a conventionalsliding bearing or provide a relatively low retention force due to theintrinsic low coefficient of friction of the low friction material.

The tolerance ring may provide sliding force control (e.g., axial orrotational) when used between mating components such as steering columnlock mechanisms. The tolerance ring prevents overload by allowingrotation between components once a threshold torque level has beenreached. For example, in steering column energy absorption systems, atolerance ring allows axial slippage to occur once an axial force levelis reached.

In general, waves having a lower stiffness generate a low torque bearingand higher stiffness waves generate higher torques, such as for doorhinge applications. These types of performance may be achieved bydesigning the tolerance ring waves to have spring characteristics thatgenerate the correct level of radial force that, when combined with thefriction characteristics of the assembly, produce the desired slidingforce levels.

The elastic/plastic nature of the wave spring characteristics is used tolimit the force variation experienced across the typical dimensionaltolerances of the assembly. This maintains a reasonably consistentsliding force. Manipulation of forces is achieved by design of wavegeometry, material thickness and hardness. To cope with componentdimensional tolerances, the tolerance ring waves are typically designedto be compressed by an amount greater than the tolerance on theclearance in which the waves are installed.

A limitation exists where relatively low sliding or rotational forcelevels are required (such as in steering column adjustment mechanisms),or where the tolerance ring acts as a pivot bush. In these applicationsforces are generally too high and radial stiffness too low. It ispossible to reduce the stiffness of the tolerance ring waves to limitmaximum forces, but this can result in assemblies with low radialload-carrying capability. Even with relatively low stiffness waves thesliding force level produced may be too high.

In other embodiments, the low friction layer may comprise materialsincluding, for example, a polymer, such as a polyketone, polyaramid, athermoplastic polyimide, a polyetherimide, a polyphenylene sulfide, apolyethersulfone, a polysulfone, a polyphenylene sulfone, apolyamideimide, ultra high molecular weight polyethylene, athermoplastic fluoropolymer, a polyamide, a polybenzimidazole, or anycombination thereof. In an example, the thermoplastic material includesa polyketone, a polyaramid, a polyimide, a polyetherimide, apolyamideimide, a polyphenylene sulfide, a polyphenylene sulfone, afluoropolymer, a polybenzimidazole, a derivation thereof, or acombination thereof. In a particular example, the thermoplastic materialincludes a polymer, such as a polyketone, a thermoplastic polyimide, apolyetherimide, a polyphenylene sulfide, a polyether sulfone, apolysulfone, a polyamideimide, a derivative thereof, or a combinationthereof. In a further example, the material includes polyketone, such aspolyether ether ketone (PEEK), polyether ketone, polyether ketoneketone, polyether ketone ether ketone, a derivative thereof, or acombination thereof. An example fluoropolymer includes fluorinatedethylene propylene (FEP), PTFE, polyvinylidene fluoride (PVDF),perfluoroalkoxy (PFA), a terpolymer of tetrafluoroethylene,hexafluoropropylene, and vinylidene fluoride (THV),polychlorotrifluoroethylene (PCTFE), ethylene tetrafluoroethylenecopolymer (ETFE), ethylene chlorotrifluoroethylene copolymer (ECTFE), orany combination thereof. In an additional example, the thermoplasticpolymer may be ultra high molecular weight polyethylene.

Lubrication of the sliding surface (e.g., with oil or grease) may beused in high force applications. Exemplary solid lubricants may includemolybdenum disulfide, tungsten disulfide, graphite, graphene, expandedgraphite, boron nitride, talc, calcium fluoride, cerium fluoride, or anycombination thereof. An exemplary ceramic or mineral includes alumina,silica, titanium dioxide, calcium fluoride, boron nitride, mica,Wollastonite, silicon carbide, silicon nitride, zirconia, carbon black,pigments, or any combination thereof.

A combination of the spring characteristics of the tolerance ring-typecore with the low friction/lubrication characteristics of a low frictioncompound-based outer surface provides a lower friction slidinginterface. This design enables tolerance rings to be designed to operateon a higher torque level for sliding bearing applications, and overwider clearances with higher radial load strength and lower slidingforces than are possible with conventional tolerance rings.

Applications for such embodiments include, for example, hinge assembliesfor portable electronics such as laptop computers and cellulartelephones. These applications require hinge mechanisms that provide alow retention force at a well-defined torque over the lifetime of theproduct. Traditional bearings do provide a low retention force as wellas a well-defined initial torque. However, with the invention, thetorque value may be kept relatively constant over the product lifetimedue to the spring adjust function of the spring steel waves combinedwith low wear of the low friction layer. In contrast, traditionaltolerance rings provide a strong retention force but with high friction.

This written description uses examples, including the best mode, andalso to enable those of ordinary skill in the art to make and use theinvention. The patentable scope of the invention is defined by theclaims, and may include other examples that occur to those skilled inthe art. Such other examples are intended to be within the scope of theclaims if they have structural elements that do not differ from theliteral language of the claims, or if they include equivalent structuralelements with insubstantial differences from the literal languages ofthe claims.

We claim:
 1. A tolerance ring comprising: an annular band formed from ametallic material wherein the metallic material consist of a sheetcomprising a plurality of circular perforations, the circularperforations evenly distributed across the sheet and the sheet shaped toinclude a sheet profile, the sheet profile including waves, cones, orball shapes, wherein the annular band is located completely within a lowfriction layer such that no portion of the annular band is exposed fromand external to the low friction layer; an elastomeric layer on theannular band; and the low friction layer on at least one of the annularband and the elastomeric layer, wherein the low friction materialcomprises a polymer selected from the group consisting of a polyketone,a polyaramid, a thermoplastic polyimide, a polyetherimide, apolyphenylene sulfide, a polyethersulfone, a polysulfone, apolyphenylene sulfone, a polyamideimide, ultra high molecular weightpolyethylene, a fluoropolymer, a polyamide, a polybenzimidazole, and anycombination thereof.
 2. A tolerance ring according to claim 1, whereinthe annular band is formed from spring steel and the low friction layeris laminated to at least one side of the annular band.
 3. A tolerancering according to claim 1, wherein the low friction layer is on theannular band opposite the elastomeric layer.
 4. A tolerance ringaccording to claim 1, wherein the low friction layer comprises PTFE andis bonded to one of the annular band and the elastomeric layer, and theelastomeric layer comprises one of nitrile rubber, olefinic elastomeric,polyether-/polyester-elastomeric, ethylene-propylene-elastomeric,ethylene-acrylic rubber and fluoro elastomeric materials.
 5. A tolerancering according to claim 1, further comprising an adhesive or primerlayer between the annular band and the elastomeric layer, and betweenthe low friction layer and said at least one of the annular band and theelastomeric layer.
 6. An assembly, comprising: an outer component; aninner component located in the outer component and movable relativethereto; a tolerance ring mounted between the inner and outercomponents, the tolerance ring comprising: an annular band formed from ametallic material and having radial inner and outer surfaces, whereinthe metallic material consist of a sheet comprising a plurality ofcircular perforations, the circular perforations evenly distributedacross the sheet and the sheet shaped to include a sheet profile, thesheet profile including waves, cones, or ball shapes, wherein theannular band is located completely within a low friction material suchthat no portion of the annular band is exposed from and external to thelow friction material; and the low friction material encapsulating theannular band, such that both the radial inner and outer surfaces aresubstantially located within the low friction material, wherein the lowfriction material comprises a polymer selected from the group consistingof a polyketone, a polyaramid, a thermoplastic polyimide, apolyetherimide, a polyphenylene sulfide, a polyethersulfone, apolysulfone, a polyphenylene sulfone, a polyamideimide, ultra highmolecular weight polyethylene, a fluoropolymer, a polyamide, apolybenzimidazole, and any combination thereof.
 7. An assembly accordingto claim 6, wherein at least a portion of the annular band is exposedfrom and extends externally relative to the low friction material.
 8. Anassembly according to claim 6, wherein the annular band is spring steeland is perforated or stamped.
 9. An assembly according to claim 6,wherein the annular band is encapsulated within the low frictionmaterial by calendaring or laminating.
 10. An assembly according toclaim 6, wherein the low friction material forms a smooth cylindricalprofile, and the annular band undulates in a non-cylindrical profilewithin the smooth cylindrical profile.
 11. An assembly according toclaim 6, wherein the low friction material and the annular band eachhave non-cylindrical profiles and are complementary in shape to eachother.
 12. An assembly according to claim 6, further comprising abacking layer joined to the tolerance ring, the backing layer is formedfrom one of steel, Al, Cu and Ti, and is radially external to the lowfriction layer, and the low friction layer is laminated on the backinglayer.
 13. An assembly according to claim 6, wherein the low frictionlayer has a thickness of approximately 0.1 to 0.05 mm on each of theradial inner and outer surfaces of the annular band, and the lowfriction layer is bonded or welded to the annular band.